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Los catalizadores heterogéneos no necesitan ser tan "heterogéneos": nanocristales Pt monodispersos mediante la
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Journal of the American Chemical Society
|January 29, 2013
Resumen
Se sintetizaron y purificaron nanocristales de platino (Pt) de alta pureza con facetas controladas. Estos catalizadores modelo revelan la reactividad dependiente de la faceta en varias reacciones catalíticas, ofreciendo información sobre la catálisis a nanoescala.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- La catálisis es la catálisis.
- Nanotecnología La nanotecnología es la nanotecnología.
Sus antecedentes:
- Si bien se estudian superficies de platino (Pt) bien definidas, los catalizadores industriales usan nanopartículas para una gran superficie.
- La comprensión de la catálisis a nanoescala es crucial para el desarrollo de catalizadores industriales eficientes.
- Se necesita una comparación directa de las facetas a nanoescala ({111} y {100}).
Objetivo del estudio:
- Desarrollar un método sintético general para la preparación de nanocristales Pt con diversas morfologías.
- Para purificar los nanocristales Pt sintetizados para la comparación directa de la reactividad de las facetas.
- Para investigar el comportamiento catalítico de {111} y {100} facetas en varias reacciones.
Principales métodos:
- Síntesis general de nanocristales Pt con diversas morfologías.
- Purificación utilizando el efecto de "autolimpieza" a través de la "recristalización coloidal" de los supercristales de Pt.
- Prueba de rendimiento catalítico en electrooxidación de ácido fórmico, oxidación de CO y reacciones de transferencia de electrones.
Principales resultados:
- Los octaedros Pt exhiben una tolerancia superior al envenenamiento en la electrooxidación del ácido fórmico en comparación con los cubos Pt.
- La oxidación de CO en los nanocristales Pt es estructuralmente insensible a bajas proporciones de O2/CO pero sensible en condiciones ricas en O2.
- Los octaedros Pt muestran una energía de activación más baja que los cubos Pt para la reacción de transferencia de electrones hexacianoferrato (III) / tiosulfato.
Conclusiones:
- Los nanocristales Pt de alta calidad con facetas selectivamente expuestas {111} y {100} sirven como sistemas modelo ideales para la catálisis a nanoescala.
- Se observó una reactividad dependiente de los factores en las reacciones de electrocatálisis, fase gaseosa y fase líquida.
- Este trabajo une la comprensión entre las superficies extendidas y la catálisis de nanopartículas.
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